Enda Walsh laughs and holds his head in his hands. He's talking about his short play, My Friend Duplicity. "It's about my relationship with 'my work'," says the Irish playwright of the piece, the first of two new Walsh dramas being performed in Edinburgh this month. "Oh my God. All I am doing is sitting at a desk all day dreaming up scenarios. How fucking ludicrous."
So what happens in the play? "An old guy and a younger woman come to my house and sit at my desk and basically do what I do: it's all the things that go through my head when I climb up to my office at 10 past nine." He laughs again. "As much as I want to live in the real world, I can only operate properly in my imagination, which I hate. So 85% of me is thinking, 'What's the point?' And the remaining 15% is enough to keep me going. It's a stupid way to live your life."
Out of this mental stew have come some of the most exciting plays to have been staged at Edinburgh in recent years. The Walworth Farce in 2007 was a painfully claustrophobic piece about two sons, trapped in a flat in London, forced to re-enact the circumstances in which they left their native Cork. The following year came The New Electric Ballroom, a companion piece, set in an Irish fishing village. Its main characters are ageing sisters who endlessly recount the events of an evening, long ago, at a dance. The plays were freighted with sadness, cruelty and regret – but made sparkling and joyous by Walsh's heartstopping verbal acrobatics and often ludicrous wit.
If those two plays were about people trapped in their own narratives, Penelope, the other new Walsh work being staged at Edinburgh, has its characters embroiled in Homer's Odyssey. These people are the "suitors", those unpleasant creatures who, in Homer, colonise Odysseus's estates in his 20-year absence, vying for Penelope's hand – before being dispatched in a gruesome bloodbath by the returning hero.
In Walsh's play, which was premiered at Galway last month, the suitors are confined in (or confine themselves to) an empty swimming pool next to Penelope's house. If there is a world beyond this, it is mentally or physically unreachable. "I have always been interested in the suitors," says Walsh. "They are so underwritten. You have this poem full of sweeping geography and bright colours and heroic quests – and then this pathetic group of conniving guys. You wonder, 'After all this time, what's happened to their waistlines? Their libidos?'"
In a sense, Penelope has a great deal in common with Greek drama: like most ancient tragedies, it starts with a small idea in Homer and builds outwards; the characters are even given a darkly foreboding dream, the harbinger of violence to come. But it is also wildly funny: its ruined characters – parodies of middle-aged male delusion – strut their stuff in swimwear around a barbecue that (metaphor alert) they are unable to light. "It's so male, it's so pathetic," says Walsh. "You see it every summer. You think, 'You don't know your way around a kitchen and here you are strutting around a barbecue.' A man painted the Sistine Chapel, and yet here we are round the barbecue."
Walsh, 42, lives in London with his wife and daughter. He was born in Dublin, and at school was taught English by Roddy Doyle. As a boy, he "wrote stories for myself and semi-romantic poetry for whatever girl I was in love with". He trained as a film editor but had an urge, he says, to "show" something. He moved from Dublin to Cork and found a way to write. "They are the Irish Texans," he says of the natives of Cork. "They fucking hate everyone else. They talk – no, they proclaim – more than everyone else. For a guy wanting to write, it was very fertile ground. And after Disco Pigs [his 1997 breakthrough], I was given the freedom of the city."
Walsh has written for the screen, notably co-scripting Steve McQueen's Hunger, which won the Camera d'Or at Cannes in 2008. But he shows no sign of being seduced away from the stage. "Everything about it shouldn't work," he says of theatre. "It's ludicrous, stupid. It's pretend. Here's a set pretending to be a swimming pool. It's a complete house of cards, for God's sake. It only works because the audience wants it to. It's bizarre, our need to have people tell us a story. And beautiful. I'm in too deep to stop now."